In recent years, photochromic lenses utilizing organic photochromic dyes have been sold as eyeglasses (for example, see WO2005/014717A1 or English language family members US2006/264593A1 and U.S. Pat. No. 7,763,693, which are expressly incorporated herein by reference in their entirety). They develop color in the bright outdoors, having the similar antiglare effect as high-concentration color lenses, and revert to high transmittance when moved indoors.
Photochromic lenses are required to quickly respond and develop highly concentrated color when prescribed light enters, and to rapidly lose the color when placed in an environment where such light is absent. Conventionally, the response rate of the color development/loss and the concentration of the color of a photochromic lens are thought to depend on intrinsic characteristics of the photochromic dye resulting from its molecular structure. Thus, the use of photochromic dyes having specific molecular structures has been studied to improve the response properties (response rate and color concentration) of photochromic films to light.
By contrast, it has been reported in recent years that the photochromic dyes in a photochromic film tend to function more readily and the color development/loss response rate and coloration concentration thereof are greatly enhanced by imparting suitable flexibility (fluidity) to the film (see WO2008/001578A1 or English language family members US2009/316246A1 and U.S. Pat. No. 7,999,989, which are expressly incorporated herein by reference in their entirety).
In a photochromic lens, a hardcoat layer is normally provided over the photochromic layer to ensure the durability of the lens. Providing such a hardcoat layer is particularly effective for increasing the durability of the lens when a suitable degree of flexibility is being imparted to a photochromic film, as described in WO2008/001578A1. Hardcoat layers formed from organic hardcoat liquids (organic hardcoat layers) can be readily formed with high hardness, and thus are widely employed in such applications.
However, the results of extensive research conducted by the present inventor have revealed that in a photochromic lens in which an organic hardcoat layer has been formed on a photochromic layer, the lens sometimes clouds, compromising optical characteristics.